Lubricating composition



Patented Jan. 15, 1%63 3,073,782 LUERTCATTNG COMPQSETXQN Earl L. Humphrey, Verona, and Qhnrles E. Trautman,

Cheswiek, Pm, assignors to Gulf Research at Bevelopment ompany, Pittsburgh, Pa, in corporation of Delaware No Drawing. Filed June 6, 1966, Ser. No. 33,936 6 Claims. (Cl. 252-54) This invention relates to an improved lubricating composition and more particularly to a lubricating composition having a high load-carrying capacity.

The current trend in designing more efiicient and economical aircraft engines, particularly combustion turbine engines of the turbo-prop type, has accentuated the need for lubricants which will effectively lubricate bearings operating at high rotational speeds and high temperatures. Lubricants for such turbine engines must possess good oxidation stability, be fluid at low temperatures, be non-corrosive, have low volatility, be resistant to thermal degradation and have good load-carrying properties. While considerable progress has been made in producing improved aircraft lubricants having a majority of these properties, some difiiculty has been experienced in producing a lubricant which meets the load-carrying requirement at the high temperatures and pressures encountered in the bearings of combustion turbine engines. Under some conditions, there is complete failure of lubrication. Failure of a composition to supply a lubricating film between engine working surfaces resulting in undue wear, scoring and, in some instances, even seizure of the adjacent surfaces.

We have discovered that a lubricating composition having improved load-carrying characteristics can be obtained by incorporating into a lubricating oil a small amount of hexachlorobicycloheptene carbinol. Thus, the improved lubricating composition of our invention comprises a major amount of a lubricating oil and a small amount of hexachlorobicycloheptene carbinol.

Hexachlorobycycloheptene carbinol [l,2,3,4,7,7-hexachloro hydroxymethyl bicyc1o-(2.2.1)-2-heptene] is available commercially and therefore neither the compound per se, nor its method of preparation constitutes any part of this invention. The amount of hexachlorobicycloheptene carbinol used can vary over wide limits depending upon the particular oil with which it is blended and upon the severity of the conditions to which the final lubricating composition is subjected. In any event, hexachlorobicycloheptene carbinol is added to the lubricating oil in an amount suflicient to impart improved loadcarrying properties to the oil. In general, this amount is about 0.5 to about 10 percent by weight, based on the weight of the oil. In most instances, optimum load-carrying characteristics are obtained with about 1 to about 4 percent by weight of the additive.

The lubricating oil in which hexachlorobicycloheptene carbinol is incorporated can be either a mineral oil or a synthetic oil depending upon the particular use for which the ultimate composition is designed. Thus, various base oils can be used depending upon whether the lubricant is intended for use in a turbo-prop engine, turbojet engine, gas turbine, automobile transmission, differential, transaxle, gear box, or the like. When a mineral oil is used, it can be derived from paratfinic, naphthenic or asphalt base oils. Hydrotreated mineral oils, because of their improved stability over untreated oils are suitable lubricating bases for preparing lubricants to be used under moderately elevated temperatures. Where temperatures majority of the lubricating characteristics of mineral oils of lubricating grade which have been synthesized by .known chemical procedures. Thus, the term synthetic oil includes esters of dibasic acids, esters of glycols with monobasic acids, polymerized olefins, copolymers of alkylene glycols and alkylene oxides, polyorgano siloxanes and the like. The lubricating oil content of the composition of this invention will vary depending upon the particular oil employed and the ultimate use for which the composition is intended. In general, the lubricating oil content comprises about 90 to 99 percent by weight of the total composition. in some instances, however, particularly where the lubricant contains other additives in combination with hexachlorobicycloheptene carbinol, the oil content may be in the order of about 80 to 95 percent by weight of the total composition.

A synthetic lubricating oil which is preferred in preparing a turbo-prop engine lubricating composition is a substantially neutral ester of an aliphatic dibasic acid, said ester containing a total of about 18 to about 40 carbon atoms in the molecule and having a majority of the properties of a mineral oil of lubricating grade. If desired, a mixture of esters having an average of about 18 to about 40 carbon atoms per molecule can be employed instead of a single ester. To produce a lubricating composition which is stable and which is substantially noncorrosive to metals, we employ esters preferably having a neutralization number below about 0.2.

The esters of the aliphatic dibasic acids can be prepared by esterifying a dibasic acid having 2 to 10 carbon atoms per molecule with an alcohol containing 2 to 18 carbon atoms per molecule, the particular acid and alcohol within these ranges being selected to give an ester lubricant containing a total of about 18 to about 40 carbon atoms per molecule. A preferred group of esters are those obtained by esterifying a dibasic acid having 6 to 10 carbon atoms per molecule with an alcohol containing 6 to 18 carbon atoms per molecule. The branched chain alcohols are especially preferred.

Specific examples of some of the alcohols which can be used in preparing the dibasic acid esters mentioned above are l-butanol; Z-butanol; 2-methyl-2-propauol; l-pentanol;

Car

in the order of 400 F. and above are to be encountered,

synthetic oils form a preferred class of lubricating bases because of their high thermal stability. By the term synthetic oil we intend to include compositions having a Z-pentanol; Z-methyI-Z-butanol; l-hexanol; 2-hexanol; 3-

hexanol; Z-methyl-l-pentanol; 3-methyl-l-pentanol; 4- methyl-l-pentanol; 2,4-dimethyl-2-pentanol; 2,3-dimethyl- 3-pentanol; 2,4-dimethyl-3-pentanol; 3-ethyl-3-pentanol; Z-methyLl-hexanol; S-methyl-l-hexanol; Z-methyl-Z-hexanol; 5-methyl-2-hexanol; 3-methyl-3-hexanol; 5-methyl-3 hexanol; l-h-eptanol; Z-heptanol; 4-heptanol; 2-methyl-2- heptanol; 3-methyl-2-heptanol; 4-methyl-4-heptanol; 2- ethyl-l-hexanol; 3-ethyl-3-hexanol; 3-ethyl-2-methyl-3- pentanol; l-octanol; 2-octanol; 2-methyl-2-octanol; 2,6-dianethyll-heptanol; 4 ethyl-4-heptanol; 3-ethyl-5-methyl-3- heptanol; l-nonanol; Z-nonanol; 3-nonanol; 4-nonanol; 5- nonanol; Z-methyl-l-nonanol; 3,7-dimethyl-l-octanol; 3- ethyl-3-octanol; 4-propyl-4-heptanol; 3-isopropyl-5-methyl-l-hexanol; l-decanol; 4-decanol; lauryl alcohol; myristic alcohol; cetyl alcohol; stearyl alcohol; glycol; glycerol; and the like, as wellas mixtures of two or more of such alcohols.

The so-called oxo octyl alcohols, which, as is'known,

are highly branched-chain saturated aliphatic m'onohydric I alcohols prepared by the One process exemplify a class of commercially available alcohol mixtures which are suitable for use in preparing synthetic lubricating oils of the invention. The Oxo process, briefly, involves the hydroformylation of olefinic hydrocarbons, followed by bydrogenation of the carbonylic compounds thus obtained. Normally, the olefinic hydrocarbons used in the manufacture of oxo-octyl alcohols are prepared by condensation of C and C olefins in the usual proportion in which they occur in petroleum refinery gases. In this case, oxo-octyl alcohols normally will contain a mixture of branchedchained isomers of octyl alcohol, and the mixture will consist mostly of isomeric dimethylhexanols. Although the above-indicated composition is the most common for x0- octyl alcohols, it will be appreciated that the proportions of the mixed isomeric alcohols can be varied to some extent by varying the proportions of the C and C olefins used in preparing the C olefin to be hydroformylated.

Specific examples of some of the dibasic acids with which the above-enumerated alcohols can be reacted in preparing the ester lubricants for use in the compositions of the present invention are oxalic, malonic, succinic, isosuccinic, glutaric, ethyl malonic, pyrotartaric, adipic, pimelic, suberic, azelaic, sebacic, and phthalic acid. When an acid having 6 to 10 carbon atoms in the molecule is esterified, an alcohol having 6 to 16 carbon atoms in the molecule is preferred in order to produce an ester having a total of 18 to 40 carbon atoms in the molecule. While the diesters ofthe aliphatic dibasic acids are preferredin preparing a turbo-prop lubricant, the esters of aromatic dibasic acids such as the phthalic acid ester of a material such as castor oil or other high molecular weight alcohols can be used in preparing other lubricants.

Specific examples of preferred synthetic lubricants to which hexachlorobicycloheptene carbinol is added to produce compositions for lubricating gears in turbo-prop engines are the substantially neutral esters of hexyl, octyl, decyl, lauryl, tridecyl, myristic and cetyl alcohols and adipic, pimelic, suberic, azelaic and sebacic acids. Specific examples of especially effective ester lubricants are diisodecyl adipate, di-Z-ethylhexyl azelate, di-2-ethylhexyl sebacate, di-isooctyl azelate, di-isooctyl sebacate, di-(tridecyl) azelate, and mixtures of two or more of such esters.

The esters can be prepared by any of the methods known in the art. According to one method, as described in US. Patent No. 2,091,241, which issued on August 24, 1937, to H. M. Kvalnes, a dicarboxylic acid or its anhydride is dissolved in an inert solvent, after which the resulting mixture is heated to its boiling point. While maintaining the mixture at its boiling point, an alcohol to give the desired ester is added gradually. When addition of the alcohol is completed, the solvent is distilled off and esterification is carried out at a temperature above 150 C. According to another suitable method, the alcohol and acid are reacted at an elevated temperature in the presence of a sulfuric acid catalyst. As the reaction proceeds, water is continuously removed by azeotropic distillation with a solvent such as benzene or toluene. When the reaction is substantially complete, the product is washed with dilute alkali to remove any acidic substances. Purification of the product may be accomplished by fractional distillation.

The lubricating composition of our invention can contain minor amounts of other agents normally added to lubricating oils for a specific purpose such an antioxidant, dispersant, detergent, pour point depressant, corrosion inhibitor, viscosity index improver, antifoamant, and the like. The lubricating composition can also contain other oiliness and extreme pressure agents to further enhance the wear characteristics when desired.

In preparing our improved lubricant, hexachlorobicycloheptene carbinol can be incorporated in the oil according to several embodiments. According to one embodiment, substantially pure hexachlorobicycloheptene carbinol as such, is added to the lubricating oil. According to another embodiment, an acetone or benzene solution of hexachlorobicycloheptene carbinol is added to the lubricant after which the acetone or benzene is selectively removed. Acetone is the preferred solvent for use with synthetic oils; benzene is preferred with mineral oils. A still further embodiment comprises preparing an oil concentrate containing relatively high concentrations of hexaclilorobicycloheptene carbinol. The concentrate thus formed can then be added to the lubricating oil by a simple blending procedure. In forming concentrates of the hexachlorobicycloheptene carbinol, it is advantageous to use an oil or other solvent lighter in viscosity than the oil to be improved. These methods of incorporating hexachlorobicycloheptene carbinol in the lubricating oil are illustrative only and do not, per se, constitute a part of the invention.

In order to illustrate the improved load-carrying characteristics of the lubricating composition of our invention, comparative tests were made using (1) Falex seizure test, (2) precision four ball wear test, (3) Ryder gear test and (4) SAE lubricant test.

FALEX SEIZURE TEST In conducting the Falex seizure test the seize point of the base oil is compared with the seize point" of samples of the same oil containing small amounts of the additive. The seize points are indicative of the loadcarrying characteristics of the lubricant being tested. In this test a Falcx lubricant testing machine is employed. This machine is essentially a device in which a small round standard pin is rotated between two standard alloy V-shaped bearing blocks. Suitable means for applying pressure to the blocks is provided by a large ratchet wheel which can be turned one tooth at a time up to the desired load. In conducting the test, about 50 cc. of the lubricant to be tested is placed in an adjustable cup which is raised so that the pin and V-blocks are completely immersed in the oil. The pin is then started rotating at 290 rpm. and the ratchet wheel is turned until a force of 250 pounds on the bearing surface is indicated on a suitable gauge. Under these conditions, a break-in run of 10 minutes is made. After the 10 minute break-in period the ratchet wheel is further turned until the bearing load is 300 pounds. The pressure is thereafter increased every 3 minutes in pound increments until the pin seizes or until a maximum load of about 4500 pounds is reached. The seize point is characterized by sudden increase of torque which is observed on a torque indicator operated in conjunction with the rotating pin. The test result is expressed as the bearing load at Which seizure occurs.

In illustrating the improved load-carrying characteristics of a composition of the invention by the Falex seizure test, a mineral oil having a viscosity of about 320 SUS at 100 F. was compared with the same base oil, containing 0.75 to 3.0 percent by weight of hexachlorobicycloheptene carbinol. The results obtained are set form in Table 1.

Table 1 Lubricating composition:

Mineral oil Mineral oil +0.75 percent by weight of hexachlorobicycloheptene carbinol 1750 Mineral oil +1.5 percent by weight of hexachlorobicycloheptene carbinol Mineral oil +3.0 percent by weight of hexachlorobicycloheptene carbinol 4000 From the above test results shown in Table 1 it can be seen that the compositions containing hexachlorobicycloheptene carbinol have load-carrying capacities considerably abovethe load-carrying capacity of the base mineral oil.

PRECISION FOUR BALL WEAR TEST In conducting this test, a precision four ball wear test machine is employed. This machine is designed so that three balls are fixed in a horizontal plane in a cup while a fourth ball which is movable is rotated in a fixed position contacting the other three balls to form an equilateral tetrahedron. The test cup is placed on a stage which can move vertically to facilitate loading. The stage rests on a calibrated fulcrum so that specific weights may be applied to force the three balls in the cup to contact the rotating fourth ball at a predetermined pres- Seizure load, lbs. 1000 sure. The cup holding the three balls also contains the test lubricant at a level of 2 mm. above the balls, thus assuring an adequate supply of lubricant at the contact points. A fixed oil temperature is maintained by a relay system connected to a thermocouple in the cup and a heater in the stage. The fourth ball can be rotated from a motor drive at 600, 1200, or 1800 rpm. Each test is run with new steel balls.

A test is run on a lubricant at a specific load, temperature, speed and time. Lubricating properties are evaluated from 1) the diameter of the scars on the three balls and (2) on the load in kilograms at which seizure occurs. A more complete description of the machine and test method are given in the Naval Research Laboratory Report entitled A Study of the Four Ball Wear Machine, by W. C. Clinton, NRL Report 3709, September 1950.

In illustrating the improved load-carrying characteristics of a composition of the invention by the precision four ball wear test, the movable ball was rotated at 1800 rpm. for one hour while increasing the lever load to 50 kilograms. The test lubricant was maintained at 110 C. The lubricants which were tested consisted of a mineral oil having viscosity of about 320 SUS at 100 F.

and the same base oil containing 0.25 to 3.0 percent by weight of hexachlorobicycloheptene carbinol. The advantageous load-carrying properties of the oil containing hexachlorobicycloheptene carbinol as compared with the base oil are illustrated by the data set forth in Table 2.

T able 2 Average Wear Scar Diameter in mm. at kg loads of- Lubricating Composition Mineral oil 0. 61 0.60 0. 65 Mineral oil 0.25 per cent by weight of hexachlorobicycloheptene carbin01 0. 80 0.88 Mineral oil 0.75 per cent by weight of hexachlorobicycloheptene carbinol 0. 78 0. 83 0.83 Mineral oil 1.5 per cent by weight of hcxachlorobicycloheptene carbi- -no1 0. 83 0. 90 0.94 Mineral oil 3.0 per cent by weight of hexachlorobicycloheptene carbin01 0.75 0.98 1.02

l Seizure at 38 kg. load.

It is apparent from the data shown in Table 2 that whereas both the mineral oil and the mineral oil containing hexachlorobicycloheptene carbinol gave satisfactory lubrication under loads up to about 30 kilograms, the mineral oil failed at 38 kilograms as evidenced by the seizure. There was no seizure when using the base oil containing from 0.25 to 3.0 percent by weight of hexachlorobicycloheptene carbinol even at loads up to 50 kilograms.

RYDER GEAR TEST The Ryder gear test is conducted in a four-square power-circulating gear machine that is loaded hydraulically after the machine has obtained operating speed. The test oil section has a two-gallon capacity and standard Ryder test gears are used.

The test lubricant is supplied through a single jet to the unmeshed side of the test gears. The test gears are loaded first to 5 p.s.i. load oil pressure, equivalent to 370 p.s.i. tooth load, and then at successive increments of 5 p.s.i. until at least 40 percent of the total working area is scufied. The duration of each loading period is minutes. At the end of each loading period, the machine is stopped and each tooth of the narrow test gear is examined by means of an 18 power stereoscopic microscope to determine the percent of the tooth area scufied. A curve of the average percent tooth area scuffed versus the load oil pressure is then drawn, from which the load oil pres- The operating conditions of this test are as follows:

Test gear speed, r.p.m 10,0001100 Load carrying ability:

est oil flow ra-te, ml./min 270:5 Test oil temperatures, F :5 Support oil temperature, F 1651-5 The criterion of the lubricating rating is the tooth load at which 22.5 percent working tooth area is scufi'cd.

In illustrating the improved load-carrying characteristics of a composition of the invention by the Ryder gear test, a synthetic oil, diisooctyl azelate, having a Ryder gear test value of 1300 to 1500 pounds per square inch was admixed with 2 percent by weight of hexachlorobicycloheptene carbinol. The average load-carrying capacity of the resulting composition was increased to 2365 pounds per square inch. In the Ryder gear test, the improved load-carrying lubricant also contained about 0.001 percent by weight of a polydimethyl siloxane (Dow-Corning Fluid 200) as an antifoarnant, 2 percent by weight of diphenylarnine as an antioxidant and 0.5 percent by weight of a mineral oil solution containing 16.5 percent calcium petroleum sulfonate, 33 percent barium salt of p-octylphenol sulfide and 2 percent stearyl alcohol as a combined detergent, bearing corrosion inhibitor and antioxidant.

SAE LUBRICANT TEST In this test the well-known SAE lubricant testing machine is employed. In this machine, a cylindrical test bearing is fixedly mounted on each of two horizontal rotating shafts, one above the other, positioned so that the outer peripheries of the test bearings are in line contact with each other. The shafts upon which the bearings are mounted are connected by reducing gears in a manner such that the shafts rotate in the same direction, but at different speeds. As a result, there is a sliding contact between the cylindrical test bearings. Suitable means for applying pressure to the test bearings is provided. The pressure between the bearings and the rate of increasing the pressure can be varied as desired. In conducting the test, the lubricant to be evaluated is placed in an adjustable cup which can be raised so that the lower test bearing is partially immersed in the lubricant. Under these conditions, a break-in run at no load is made. After the break-in period, a load is applied and increased at a constant rate until lubricant failure occurs. Failure of the lubricant is evidenced by a sudden increase or torque, tearing of the metal on the surfaces of the bearings, overheating or the like. In the test reported in Table 3, the shafts upon which the bearings were mounted rotated at a gear ratio of 3.4 to 1, the fastest rotating shaft turning at 1000 rpm. A breakin period of one minute at no load was employed. Thereafter, the load was increased at a rate of 6.5 pounds per second until lubricant failure was evidenced. The test result is expressed as the load in pounds at which failure occurred.

In illustrating the improved load-carrying characteristics of a composition of the invention by the SAE lubricant test, a synthetic lubricant was compared with the same lubricant containing 0.5 to 7.0 percent by weight of hexachlorobicycloheptene carbinol. The advantageous load-carrying properties of the lubricant containing hexachlorobicycloheptene carbinol are illustrated by the data set forth in Table 3. In the SAE lubricant test, the synthetic lubricant in each instance, contained 7 0.001 percent by weight of an antifoamant, 2 percent by weight of a mineral oil solution of a detergent, corrosion inhibitor and antioxidant.

2. A lubricating composition comprising a major amount of a mineral lubricating oil and a small amount, sufficient to improve the load-carrying characteristics of Table 3 Composition, Percent By Weight A B C D E F Diisoootyl azelate 97.5 97.0 96.5 95. 5 .5 90.5 Hcvachlorobicycloheptcne carbinol 0.5 1.0 2.0 .0 7.0 Diphenylarnine 2.0 2.0 2.0 2. 0 .0 2.0 Mineral oil solution containing 16.5%

calcium petroleum sulionate, 33%

barium salt of p-octylphcnol sulfide and 2% stearyl alcohol 0.5 0 0 5 0.5 5 0.5 Dow-Corning Fluid 200 (added) 0.001 0 001 0 001 0.001 001 0.001 SAE Lubricant Test: Speed 1000 r.p.m.; gear ratio 3.4:1: break-in 1 minute at no load; loading rate 6.5

lbS./S0c., Load failure at: lbs 120 255 260 1 Dow-Corning Fluid 200 is a polydimethyl siloxane having a viscosity of about 1000 eentistokes at 77 F.

It will be observed from the data shown in Table 3 that the synthetic lubricants containing hexachlorbicycloheptene carbinol have load-carrying capacities considerably above the load-carrying capacity of the base synthetic lubricant. It will be noted further that optimum improvement is obtained with about 2 percent by weight of the hexachlorobicycloheptene carbonol.

Typical physical characteristics of Composition D in Table 3 are as follows.

Specific gravity, 60/60 F 0.9328 Viscosity, kinematic, cs.: 4

At 100 F 13.29

At 210 F 3.47 Viscosity index 160 Cloud point, F -45 Pour point, F --75 Color, ASTM D- 3 /2 Flash point, O.C.: F 450 Fire point, O.C.: F 490 Total acid No., ASTM D664 0.12

the oil, of l,2,3,4,7,7-hexachloro-S-hydroxymethylbicyclo- (2.2.1)-2-heptene.

3. A lubricating composition comprising a major amount of a synthetic lubricating oil and a small amount, sufiicient to improve the load-carrying characteristics of the oil, of l,2,3,4,7,7-hexachloro-5-hydroxymethylbicyclo (2.2. 1 -2-heptene.

4. The lubricating composition of claim 3 wherein the synthetic lubricating oil is a substantially neutral ester of a dibasic acid containing 2 to 10 carbon atoms and an alcohol containing 2 to 18 carbon atoms, said ester con taining a total of 18 to 40 carbon atoms in the molecule.

5. A lubricating composition comprising a major amount of a substantially neutral ester of an aliphatic dibasic acid containing 6 to 10 carbon atoms and an aliphatic alcohol containing 6 to 16 carbon atoms and a small amount, suflicient to improve the load-carrying characteristics of the esters, of l,2,3,4,7,7-hexachloro-5- hydroxymethylbicyclo-(2.2.1 )-2-heptene.

6. A lubricating composition comprising a major amount of diisooctyl azelate and a small amount, sufiicient to improve the load-carrying characteristics of the diisooctyl azelate, of 1,2,3,4,7,7-hexachloro-5-hydroxymethylbicyclo- 2.2.1 )-2-heptene.

References Cited in the file of this patent UNITED STATES PATENTS Lincoln Nov. 22, 1938 Lincoln et al. July 2, 1940 OTHER REFERENCES CERTIFICATE OF CORRECTION Patent No. 3,073, 782 January 15, 1963 It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

In the grant, line 2, for "Tautman" read w Trautman column 1, line 30, for "resulting" read results line 40, for "Hexachlorobycycloheptene" read Hexachlorobicyclohepteme column 3, line 19, for "ofthe" read of the column 6, line 57, for "or" read of column 7, line 27, for carbonol read carbinol line 50, for "lubrication" read tlubricating column 8, line 38, for "esters" read es er --o ERNEST w. SWIDER DAVID LADD Afifisfing Officer Commissioner of Patents 

1. A LUBRICATING COMPOSITION COMPRISING A MAJOR AMOUNT OF A LUBRICATION OIL AND A SMALL AMOUNT, SUFFICIENT TO IMPROVE THE LOAD-CARRYING CHARACTERISTICS OF THE OIL, OF 1,2,3,4,7,7 -HEXACHLORO - 5 - HYDROXYMETHYLBICYCLO(2.2.1)-2-HEPTENE. 